Process for the production of antibiotic R106 by a strain of Aureobasidium pullulans

ABSTRACT

An antibiotic R106 represented by the general formula (I): ##STR1## wherein: R is methyl or ethyl; 
     X 1  is MePhe, β-HOMePhe or Phe; 
     X 2  is allo-Ile, Val or Leu; 
     X 3  is MeVal or Val; 
     X 4  is β-HOMeVal, γHOMeVal, MeVal, Val, N,β-MeAsp, β-HOMePhe, MePhe, MeDH 2 ,3 Val or MeDH 3 ,4 Val 
     is produced by a process which comprises culturing a strain of the genus Aureobasidium that is capable of producing the said antibiotic R106 and collecting the said antibiotic from the fermentation broth. The antibiotic R106 compounds are useful in the treatment of fungal infection.

This application is a division of application Ser. No. 379,629, filed Jul. 13, 1989 now U.S. Pat. No. 5,057,493.

The present invention relates to novel antibiotics R106 which are useful as therapeutic agents for the treatment of fungal infection, and a process for producing the same as well as for the use thereof.

As therapeutic agents for the treatment of fungal infection, there are known approximately 20 antibiotics including amphotericin B, nystatin, trichomycin, griseofulvin, pyrrolnitrin, clotrimazole, miconazole nitrate, etc. However, these antibiotics are questionable in activity and toxicity.

An object of the present invention is to provide novel antibiotics which have a high activity but low toxicity as therapeutic agents for treating fungal infection.

The present inventors isolated a number of microorganisms from the surface of plant leaves or from the soil, for purposes to discover novel antibiotics, purified antibiotics produced by these microorganisms and examined the biological properties of these antibiotics. As a result, it has been found that a series of antibiotics showing an antimicrobial activity against pathogenic fungi such as Candida albicans, Cryptococcus neoformans, etc. can be produced in fermentation broth of microorganisms belonging to the genus Aureobasidium.

These antibiotics have been isolated from the fermentation broth; and as the result of examination of physicochemical properties of the antibiotics, it has been confirmed that these antibiotics are novel compounds that are not found in the literature. These antibiotics have been named R106. Thus, the present invention provides antibiotics R106 having the following structural formula and a process for production thereof as well as application thereof: ##STR2## wherein: R is methyl or ethyl;

X₁ is MePhe, β-HOMePhe or Phe;

X₂ is allo-Ile, Val or Leu;

X₃ is MeVal or Val;

X₄ is β-HOMeVal, γ-HOMeVal, MeVal, Val, N,β-MeAsp, β-HOMePhe, MePhe, MeDH₂,3 Val or MeDH₃,4 Val.

The abbreviations for amino acids used in the above formula (I) are given in Table 9 later shown.

First, microorganisms used for the present invention can be a strain of the genus Aureobasidium which is capable of producing antibiotics R106 of the present invention represented by the general formula (I). An example of the microorganisms is Aureobasidium No. R106 (hereinafter this strain is referred to as strain No. R106), which the present inventors newly isolated from a soil sample collected at Kamitushima-cho, Kamiagata-gun, Nagasaki-ken, Japan. This strain is a new strain that has the characteristics described above and can produce advantageously novel antibiotics R106 of the present invention. Thus, this strain is one of the microorganisms which can be effectively used for the method of the present invention. Further, not only mutants of strain No. R106 which are prepared by natural or artificial mutation, but all microorganisms of the genus Aureobasidium which are capable of producing the antibiotics R106 of the present invention can be used for the method of the present invention.

Strain No. R106 has the following mycological characteristics.

(1) Growth on various nutrient media.

The following table shows cultural characteristics of strain No. R106 on various nutrient agar media after incubation for 4, 7, and 14 days at 25° C.

Strain No. R106 shows good growth on potato-dextrose agar, Czapek agar, and malt extract agar media. Colonies of the strain are usually mucoid, pasty, or rarely velvety, and then become leathery as time goes by. The colonies are white to creamy or light pink in color, then changing olive green to light brown or brown, sometimes finally to black with production of dark brown pigments, which is insoluble, as time goes by. Rhizoidlike structures are often formed around the colonies. Hyphae with a size of 2 to 15 μm in diameter elongate into the agar medium without forming aerial mycelia. Blastic conidia with a size of 1-5×2-10 μm, are often formed intercalary or terminal on hyphae like finger tips and sometimes form ball-like clusters. Vegetative cells in early stage of growth are yeast-like, and ellipsoidal or lemon-like in shape with a size of 3-5×8-15 μm and multiply by polyblastic budding. The strain forms arthrospores with a size of 4-10×8-20 μm and chlamydospores with a size of 5-25×10-25 μm. No ascospores are observed.

    ______________________________________                                                  Color of colonies after                                                                         Growth                                               Media    4-7-14 days cultivation                                                                         characteristics                                      ______________________________________                                         Malt extract                                                                            Creamy - olive green -                                                                          Good growth                                          agar     light brown      Chlamydospores                                                                 are formed.                                          Potato   Creamy - olive green -                                                                          Good growth                                          dextrose light brown      Blastic conidia                                      agar                      are abundant and                                                               form ball-like                                                                 clusters.                                            Czapek agar                                                                             Creamy - brown - black                                                                          Good growth                                                                    Hyphae are abundant,                                                           and often                                                                      thick-walled.                                        Sabouraud                                                                               Creamy - olive green -                                                                          Good growth                                          agar     dark green       Chlamydospores are                                                             observed.                                            Oatmeal agar                                                                            Creamy gray -    Moderate growth                                               light brown - dark brown                                                                        Hyphae are abundant.                                 YpSs agar                                                                               Creamy - light olive                                                                            Good growth                                                   green - olive green                                                                             Hyphae are thin.                                                               Blastic conidia are                                                            abundant and form                                                              ball-like clusters                                   ______________________________________                                    

(2) Physiological characteristics.

1) Temperature range permitting growth

Temperature permitting growth : 12.5°-29.0° C.

Optimum temperature for growth : 23.0°-29.0° C.

2) Vitamin requirement

Growth in vitamin-free medium : Good growth.

3) Pigment formation

Insoluble dark brown pigments are produced. From the foregoing mycological characteristics, strain No. R106 is considered to belong to the genus Aureobasidium. Among the known species of Aureobasidium listed in "W. B. Cooke: Mycopathlogia et Mycologia Applicata, 17 , 1-43 (1962)", "J. A. von Arx, The Genera of Fungi Sporulating in Pure Culture, J. Cramer, Lehre (1970)", G. S. de Hoog & E. J. Hermanides-Nijhoff, "Studies in Mycology" No. 15, p. 141-166, CBS, Baarn (1977) and other references, strain No. R106 is considered to be a member of A. pullulans from its characteristics. But known A. pullulans did not produce an antibiotic R106. So we designated the strain as Aureobasidium pullulans No. R106, and the strain was deposited on Jul. 8, 1988 at the Fermentation Research Institute, Agency of Industrial Science and Technology, Japan, under deposit number FERM BP-1938.

The antibiotics R106 of the present invention can be produced by inoculating and culturing the strain described above in a nutrient medium.

In culturing the R106-producing organisms, there may be appropriately used as carbon sources, for example, glucose, fructose, saccharose, starch, dextrin, glycerin, molasses, thick malt syrup, oils and fats, organic acids, etc.; as nitrogen sources, organic nitrogen compounds or inorganic nitrogen compounds such as soybean powder, cotton seed powder, corn steep liquor, casein, peptone, Casamino acids, yeast extract, meat extract, germ, urea, amino acids, ammonium salts, etc.; as salts, inorganic salts, for example, sodium salts, potassium salts, calcium salts, magnesium salts, phosphates, etc.; singly or in appropriate combination. If necessary and desired, heavy metals salts, e.g., iron salts, copper salts, zinc salts, cobalt salts, etc.; vitamins such as biotin, vitamin B1, etc.; other organic or inorganic compounds which can assist growth of the producing organisms and accelerate production of R106, may be suitably added. Furthermore, defoaming agents or surface active agents such as silicone oil, polyalkylene glycol ethers, etc. may also added to the medium.

For culture, conventional techniques used for production of antibiotics by fermentation of microorganisms may be adopted, and liquid culture methods especially by shaking or tank fermentation with aeration and agitation are most suitable. Further by appropriately supplementing carbon sources, nitrogen sources, trace salts, etc. during the course of incubation, the amount of antibiotics R106 production can be increased. A preferred temperature for the culture is generally in a range of 15 to 30° C. A pH value for the culture is preferably in a range of 2 to 8. The number of days for fermentation may vary depending upon culture conditions but is sufficient generally 1 to 14 days.

The R106 thus accumulated in the fermentation broth can be advantageously collected therefrom by utilizing the physicochemical properties of the antibiotics.

That is, antibiotics R106 are contained in the fermentation broth and mycelial cake and can thus be obtained by extracting the whole fermentation broth with a hydrophobic organic solvent, for example, an organic solvent such as ethyl acetate, butyl acetate, chloroform, butanol, methyl isobutyl ketone, etc. Furthermore, antibiotics R106 can also be obtained after separation of the fermentation broth into the broth filtrate and mycelial cake by filtration or centrifugation. For isolation of R106 from the broth filtrate, the broth filtrate may be extracted with the aforesaid hydrophobic organic solvents. Alternatively, the broth filtrate may be brought into contact with an appropriate supporting resin to adsorb R106 in the filtrate thereto followed by elution with an appropriate solvent. For the purpose, supporting resins such as, for example, activated charcoal, cellulose powder, adsorptive resin, etc., which separate compounds according to their differences in the adsorbability to the resin, can be advantageously used. In order to elute antibiotics R106 from these resins aqueous solution of hydrophilic organic solvents, for example, aqueous acetone, aqueous alcohol, etc. can be used in appropriate combination, though the combination varies depending upon kind and property of the resin. Antibiotics R106 can be obtained from the mycelial cake by extracting with a hydrophilic organic solvent such as acetone or the like.

Crude R106 thus obtained can be further purified by conventional purification methods used for lipophilic antibiotics. An example of the methods is column chromatography with a supporting resin such as silica gel, activated aluminum, activated charcoal and adsorbtive resin.

In the silica-gel column chromatography, antibiotics R106 can be eluted with chloroform, ethylacytated, methanol, acetone, water, etc. which are used singly or in appropriate combination.

Isolation and purification by high performance liquid chromatography can also be advantageously utilized. Examples of the supporting resins which can be used include silica gel, silica gel with chemical bonds such as octadecyl, octyl or amino groups, or polystyrene type porous polymer gel, etc.

As a mobile phase, there may be used a mixed solvent of hexane, isopropyl alcohol and chloroform, etc., aqueous methanol or aqueous acetonitrile, etc.

Countercurrent chromatography which is a purification method based on differences of compounds in partition between two liquid phases can also be advantageously utilized. As the partition solvent system, there may be used a solvent mixture of hexane-ethyl acetate-acetonitrile, chloroform-methanol-water or the like.

The physicochemical and biological properties of these new antibiotics R106 are as explained below by referring partly to the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the ultraviolet absorption spectrum of the compound 1, and

FIG. 2 is a graph showing the infrared absorption spectrum of the same compound.

(1) Physicochemical properties

Structures of antibiotics R106 obtained in accordance with the present invention are shown in Table 1.

                  TABLE 1                                                          ______________________________________                                          ##STR3##                                                                      Compound                                                                       No.     R      X.sub.1    X.sub.2                                                                              X.sub.3                                                                              X.sub.4                                  ______________________________________                                          1      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal β-HOMeVal                            2      CH.sub.3                                                                              MePhe      allo-Ile                                                                             MeVal β-HOMeVal                            3      C.sub.2 H.sub.5                                                                       MePhe      Val   MeVal β-HOMeVal                            4      C.sub.2 H.sub.5                                                                       MePHe      allo-Ile                                                                             MeVal γ-HOMeVal                           5      C.sub.2 H.sub.5                                                                       β-HoMePhe                                                                            allo-Ile                                                                             MeVal β-HOMeVal                            6      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             Val   β-HOMeVal                            7      C.sub. 2 H.sub.5                                                                      MePhe      allo-Ile                                                                             MeVal MeVal                                     8      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal Val                                       9      C.sub.2 H.sub.5                                                                       MePhe      Leu   MeVal β-HOMeVal                           10      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal N,β-MeAsp                           11      CH.sub.3                                                                              MePhe      allo-Ile                                                                             MeVal MeVal                                    12      C.sub.2 H.sub.5                                                                       MePhe      Val   MeVal MeVal                                    13      C.sub.2 H.sub.5                                                                       Phe        allo-Ile                                                                             MeVal MeVal                                    14      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal MeDH.sub.3,4 Val                         15      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal β-HOMePhe                           16      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             Val   MeVal                                    17      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal MePhe                                    18      C.sub.2 H.sub.5                                                                       MePhe      allo-Ile                                                                             MeVal MeDH.sub.2,3 Val                         ______________________________________                                    

Abbreviations for the amino acids in Table 1 are indicated in Table 9 later presented.

Physicochemical properties of compound 1 are as follows.

(1) Molecular formula: C₆₀ H₉₂ N₈ O₁₁

(2) Elemental analysis: C 65.0%, H 8.5%, N 9.9% (found); C 65.45%, H 8.36%, N 10.18% (calcd.)

(3) Melting point: 138°-140° C.

(4) Specific rotary power: [α]_(D) ²⁰ -254.3 (C 1.0, methanol)

(5) Molecular weight: FAB-MS m/z 1101 (M+H), 1123 (M+Na)

(6) Ultraviolet absorption spectrum (in methanol): as shown in FIG. 1

(7) Infrared absorption spectrum (KBr method): as shown in FIG. 2

(8) Amino acid analysis: Proline, alloisoleucine, leucine and phenylalanine are detected (device: JCL-300 manufactured by JEOL Co., Ltd.; Detection: ninhydrin reaction)

(9) Color forming reaction: positive in 50% sulfuric acid and potassium permanganate and negative in ninhydrin and ferric chloride

(10) Solubility in solvent: soluble in chloroform, methanol, ethanol, N,N-dimethylformamide and dimethylsulfoxide; sparingly soluble in water

(11) Acidic, neutral or basic: neutral substance

(12) Color: white substance

Physicochemical properties of compounds 2 through 18 are shown in Table 2.

                                      TABLE 2                                      __________________________________________________________________________     Elemental Analysis          Molecular                                          Compound                                                                             Found (%)  Calcd. (%) Weight m/z                                                                             Molecular                                  No.   C   H  N   C  H   N   (FAB-MS)                                                                               Formula                                    __________________________________________________________________________      2    64.81                                                                              8.53                                                                              10.06                                                                              65.17                                                                             8.34                                                                               10.30                                                                              1087(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.11                                     1109(M + Na)                                        3    65.09                                                                              8.61                                                                               9.96                                                                              65.17                                                                             8.34                                                                               10.30                                                                              1087(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.11                                     1109(M + Na)                                        4    65.12                                                                              8.71                                                                               9.87                                                                              65.45                                                                             8.36                                                                               10.18                                                                              1101(M + H)                                                                            C.sub.60 H.sub.92 N.sub.8 O.sub.12                                     1123(M + Na)                                        5    64.36                                                                              8.51                                                                               9.83                                                                              64.49                                                                             8.30                                                                               10.02                                                                              1117(M + H)                                                                            C.sub.60 H.sub.92 N.sub.8 O.sub.12                                     1139(M + Na)                                        6    64.63                                                                              8.65                                                                              10.20                                                                              65.17                                                                             8.34                                                                               10.30                                                                              1087(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.11                                     1109(M + Na)                                        7    66.25                                                                              8.69                                                                              10.31                                                                              66.39                                                                             8.54                                                                               10.32                                                                              1085(M + H)                                                                            C.sub.60 H.sub.92 N.sub.8 O.sub.10                                     1107(M + Na)                                        8    65.87                                                                              8.60                                                                              10.34                                                                              66.14                                                                             8.47                                                                               10.46                                                                              1071(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.10                                     1093(M + Na)                                        9    65.21                                                                              8.58                                                                              10.00                                                                              65.45                                                                             8.36                                                                               10.18                                                                              1101(M + H)                                                                            C.sub.60 H.sub.92 N.sub.8 O.sub.11                                     1123(M + Na)                                       10    64.14                                                                              8.27                                                                              10.03                                                                              64.61                                                                             8.13                                                                               10.05                                                                              1115(M + H)                                                                            C.sub.60 H.sub.90 N.sub.8 O.sub.12                                     1137(M + Na)                                       11    65.61                                                                              8.84                                                                              10.41                                                                              66.14                                                                             8.47                                                                               10.46                                                                              1071(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.10                                     1093(M + Na)                                       12    66.03                                                                              8.56                                                                              10.28                                                                              66.14                                                                             8.47                                                                               10.46                                                                              1071(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.10                                     1093(M + Na)                                       13    65.82                                                                              8.52                                                                              10.16                                                                              66.14                                                                             8.47                                                                               10.46                                                                              1071(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.10                                     1093(M + Na)                                       14    66.50                                                                              8.49                                                                              10.12                                                                              66.52                                                                             8.37                                                                               10.34                                                                              1083(M + H)                                                                            C.sub.60 H.sub.90 N.sub.8 O.sub.10                                     1105(M + Na)                                       15    66.58                                                                              8.37                                                                               9.73                                                                              66.87                                                                             8.07                                                                                9.75                                                                              1149(M + H)                                                                            C.sub.64 H.sub.92 N.sub.8 O.sub.11                                     1171(M + Na)                                       16    65.94                                                                              8.58                                                                              10.29                                                                              66.14                                                                             8.47                                                                               10.46                                                                              1071(M + H)                                                                            C.sub.59 H.sub.90 N.sub.8 O.sub.10                                     1093(M + Na)                                       17    67.42                                                                              8.28                                                                               9.76                                                                              67.81                                                                             8.18                                                                                9.89                                                                              1133(M + H)                                                                            C.sub.64 H.sub.92 N.sub.8 O.sub.10                                     1155(M + Na)                                       18    66.39                                                                              8.51                                                                              10.18                                                                              66.52                                                                             8.37                                                                               10.34                                                                              1083(M + H)                                                                            C.sub.60 H.sub.90 N.sub.8 O.sub.10                                     1105(M + Na)                                       __________________________________________________________________________     Compound                                                                             Specific  Infrared Absorption cm.sup.-1                                  No.   Rotary Power[α].sub.D.sup.20                                                       (KBr method)    Amino Acid Analysis*                           __________________________________________________________________________      2    -222.3    3450, 3340, 2970, 1750, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1530, 1410, 1300, 1210, 1090, 700                                                              leucine, phenylalanine                          3    -345.0    3450, 3350, 2970, 1740, 1640                                                                   proline, valine, leucine,                            (C 0.30, methanol)                                                                       1530, 1420, 1300, 1210, 1090, 700                                                              phenylalanine                                   4    -241.3    3450, 3350, 2970, 1740, 1640                                                                   proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1540, 1420, 1300, 1200, 1090, 700                                                              leucine, phenylalanine                          5    -211.6    3450, 3340, 2970, 1740, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1530, 1420, 1300, 1210, 1080, 700                                                              leucine, phenylalanine                          6    -191.8    3470, 3330, 2980, 1740, 1640,                                                                  proline, valine, allo-                               (C 1.0, methanol)                                                                        1530, 1410, 1290, 1220, 1090, 700                                                              isoleucine, leucine,                                                           phenylalanine                                   7    -248.1    3450, 3340, 2970, 1760, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1530, 1420, 1270, 1200, 1090, 700                                                              leucine, phenylalanine                          8    -170.0    3450, 3330, 2960, 1740, 1640,                                                                  proline, valine, allo-                               (C 0.80, methanol)                                                                       1520, 1420, 1300, 1200, 1080, 700                                                              isoleucine, leucine,                                                           phenylalanine                                   9    -226.3    3500, 3320, 2990, 1750, 1640,                                                                  proline, leucine,                                    (C 1.0, methanol)                                                                        1520, 1420, 1300, 1200, 1090, 700                                                              phenylalanine                                  10    -217.6    3450, 3320, 2970, 1740, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1540, 1420, 1300, 1200, 1080, 700                                                              leucine, phenylalanine                         11    -228.1    3450, 3340, 2970, 1740, 1640,                                                                  proline, alloisoleucine,                             (C 0.70, methanol)                                                                       1530, 1420, 1300, 1200, 1090, 700                                                              leucine, phenylalanine                         12    -229.7    3450, 3330, 2970, 1740, 1640,                                                                  proline, valine, leucine,                            (C 0.31, methanol)                                                                       1530, 1420, 1300, 1200, 1090, 700                                                              phenylalanine                                  13    -210.0    3470, 3340, 2980, 1750, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1530, 1420, 1290, 1210, 1090, 700                                                              leucine, phenylalanine                         14    -205.1    3450, 3330, 2960, 1750, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1520, 1410, 1290, 1190, 1080, 700                                                              leucine, phenylalanine                         15    -256.7    3480, 3330, 2970, 1740, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1520, 1420, 1280, 1200, 1090, 700                                                              leucine, phenylalanine                         16    -215.4    3450, 3340, 2970, 1740, 1640,                                                                  proline, valine, allo-                               (C 0.44, methanol)                                                                       1530, 1420, 1300, 1200, 1080, 700                                                              isoleucine, leucine,                                                           phenylalanine                                  17    -272.9    3460, 3350, 2980, 1750, 1640,                                                                  proline, alloisoleucine,                             (C 1.0, methanol)                                                                        1530, 1420, 1280, 1220, 1090, 710                                                              leucine, phenylalanine                         18    -247.0    3460, 3330, 2970, 1740, 1640,                                                                  proline, alloisoleucine,                             (C 0.20, methanol)                                                                       1530, 1410, 1300, 1220, 1100, 700                                                              leucine, phenylalanine                         __________________________________________________________________________      *Detected by ninhydrin reaction using JCL300 manufactured by JEOL Co.,         Ltd.                                                                     

(2) Biological properties

The antibiotics R106 of the present invention are active against various fungi including pathogenic fungi. The minimum inhibitory concentration (MIC) of each antibiotic against various fungi was determined by the agar dilution method using casitone agar medium (2.0% glucose, 0.9% bacto-casitone, 1.0% yeast extract, 0.1% KH₂ PO₄, 0.1% Na₂ HPO₄, 1.0% sodium citrate, 2.0% agar: concentrations are all by w/v). The results determined with compound 1 are shown in Tables 3 and 4. The results determined with compounds 2 through 18 are shown in Table 5.

                  TABLE 3                                                          ______________________________________                                                                  Minimum Inhibitory                                    Strain        TIMM No.   Concentration (μg/ml)                              ______________________________________                                         Candida albicans                                                                             0144        0.04≧                                         Candida albicans                                                                             1529        0.04≧                                         Candida albicans                                                                             1623        0.04≧                                         Candida albicans                                                                             1308        0.04≧                                         var. stellatoidia                                                              Candida tropicalis                                                                           0312       0.08                                                  Candida tropicalis                                                                           0315       0.08                                                  Candida kefyr 0298       0.16                                                  Candida parapsilosis                                                                         0287       0.16                                                  Candida krusei                                                                               0270        0.04≧                                         Candida guilliermondii                                                                       0257       0.08                                                  Candida glabrata                                                                             1062        0.04≧                                         Candida glabrata                                                                             1064       0.08                                                  Cryptococcus neoformans                                                                      0354       0.63                                                  Cryptococcus neoformans                                                                      0355       0.31                                                  Cryptococcus neoformans                                                                      0363       1.25                                                  Cryptococcus laurentii                                                                       0352       0.31                                                  Cryptococcus terreus                                                                         0424       0.31                                                  Rhodotorula rubra                                                                            0923       0.63                                                  ______________________________________                                    

Each minimum growth inhibitory concentration was determined after culturing at 27° C. for 4 days.

                  TABLE 4                                                          ______________________________________                                                                   Minimum Inhibitory                                                             Concentration                                        Strain          TIMM No.  (μg/ml)                                           ______________________________________                                         Aspergillus clavatus                                                                           0056      0.16                                                 Aspergillus flavus                                                                             0058      >80                                                  Aspergillus nidulans                                                                           0112      0.16                                                 Aspergillus niger                                                                              0113      >80                                                  Aspergillus terreus                                                                            0120      5                                                    Aspergillus citrinum                                                                           1330      >80                                                  Aspergillus commune                                                                            1331      1.25                                                 Aspergillus crustorum                                                                          1332      >80                                                  Trichophyton mentagrophytes                                                                    1177      >80                                                  Trichophyton rubrum                                                                            1216      >80                                                  Microsporum canis                                                                              0760      >80                                                  Epidermophyton floccosum                                                                       0431      2.5                                                  Fonsecaea pedrosoi                                                                             0482      0.31                                                 Phialophora verrucosa                                                                          0903      >80                                                  Exophiala werneckii                                                                            1334      1.25                                                 Cladosporium bantianum                                                                         0343      0.63                                                 Cladosporium carrionii                                                                         0337      1.25                                                 Sporothrix schenckii                                                                           0959      >80                                                  Histoplasma capsulatum                                                                         0713      0.16                                                 Histoplasma capsulatum                                                                         0714      0.08                                                 Paracoccidioides brasiliensis                                                                  0878      80                                                   Paracoccidioides brasiliensis                                                                  0880      0.31                                                 Geotrichum candidum                                                                            0694      0.63                                                 Trichosporon cutanum                                                                           1318      >80                                                  Blastomyces dermatitidis                                                                       1690      0.04≧                                         Blastomyces dermatitidis                                                                       0126      0.31                                                 ______________________________________                                    

After culturing at 27° C. for 7 days, each minimum inbibitory concentration was determined.

                                      TABLE 5                                      __________________________________________________________________________             TIMM                                                                               Compound No.                                                       Strain  No. 2   3   4  5   6  7   8   9                                        __________________________________________________________________________     Candida 0136                                                                               0.10                                                                               0.10                                                                               0.20                                                                              0.05≧                                                                       0.78                                                                              3.12                                                                               1.56                                                                               0.05≧                             albicans                                                                       Candida 0171                                                                               0.10                                                                               0.10                                                                               0.10                                                                              0.05≧                                                                       0.39                                                                              1.56                                                                               1.56                                                                               0.05≧                             albicans                                                                       Candida 1768                                                                               0.78                                                                               1.56                                                                               0.39                                                                              0.05≧                                                                       0.39                                                                              3.12                                                                               12.5                                                                               0.20                                     albicans                                                                       Candida 0301                                                                               0.20                                                                               0.20                                                                               0.78                                                                              0.20                                                                               0.39                                                                              25  25< 0.20                                     kefyr                                                                          Candida 1062                                                                               0.20                                                                               0.20                                                                               1.56                                                                              0.20                                                                               1.56                                                                              25< 25< 0.39                                     glabrata                                                                       Cryptococcus                                                                           0354                                                                               1.56                                                                               1.56                                                                               25 3.12                                                                               25 25< 25< 25                                       neoformans                                                                     __________________________________________________________________________            TIMM                                                                               Compound No.                                                        Strain No. 10  11 12  13  14  15 16 17 18                                      __________________________________________________________________________     Candida                                                                               0136                                                                               0.78                                                                               1.56                                                                              6.25                                                                               6.25                                                                               1.56                                                                               12.5                                                                              3.12                                                                              12.5                                                                              6.25                                    albicans                                                                       Candida                                                                               0171                                                                               0.78                                                                               1.56                                                                              6.25                                                                               12.5                                                                               1.56                                                                               25 1.56                                                                              25 3.12                                    albicans                                                                       Candida                                                                               1768                                                                               12.5                                                                               1.56                                                                              25  12.5                                                                               12.5                                                                               25 25 25<                                                                               25                                      albicans                                                                       Candida                                                                               0301                                                                               3.12                                                                               6.25                                                                              12.5                                                                               25  6.25                                                                               25<                                                                               3.12                                                                              25<                                                                               25                                      kefyr                                                                          Candida                                                                               1062                                                                               3.12                                                                               25<                                                                               25< 25< 12.5                                                                               25<                                                                               25<                                                                               25<                                                                               25<                                     glabrata                                                                       Cryptococcus                                                                          0354                                                                               25  25<                                                                               25< 25< 25< 25 25<                                                                               25<                                                                               25<                                     neoformans                                                                     __________________________________________________________________________

Antibiotics R106 exhibit a potent therapeutic effect on systemic candidiasis model of mice prepared by intravenous injection of Candida albicans. Candida albicans TIMM 1768 was cultured in Sabouraud-dextrose broth at 37° C. overnight, and the cells were collected and suspended in physiological saline. A cell suspension containing 1×10⁶ cells was intravenously injected to ICR strain mice (5week age, female). After 3 hours, a solution of an antibiotic R106 in TWEEN 80-ethanolphysiological saline (1 :9 :90, v/v) was subcutaneously, intravenously or orally given to the mice in various concentrations, and then once a day for 4 days the R106 drug solution was given. Mortality was assessed for 30 days after infection to determine the therapeutic effect. The results obtained by measurement with compound 1 are shown in Table 6.

                  TABLE 6                                                          ______________________________________                                                                           Number of                                                                      Animal Survived/                                    Dose     Mean              Number of                                    Route  (mg/kg)  Survival Day                                                                              T/C (%)                                                                               Animal Tested                                ______________________________________                                         p.o.   7        14.8 ± 4.8                                                                             121    0/5                                                 14       23.2 ± 6.2                                                                             189    0/5                                                 28       30.0 ± 0                                                                               245    5/5                                          s.c.    1.75    14.2 ± 2.9                                                                             116    0/5                                                 3.5      18.8 ± 3.5                                                                             153    0/5                                                 7        22.4 ± 7.0                                                                             183    2/5                                                 14       27.2 ± 6.3                                                                             222    4/5                                          i.v.    0.875   14.6 ± 1.9                                                                             119    0/5                                                  1.75    18.2 ± 5.0                                                                             149    0/5                                                 3.5      19.2 ± 6.3                                                                             157    0/5                                                 7        29.0 ± 2.2                                                                             237    4/5                                                 14       26.6 ± 5.0                                                                             217    3/5                                          Control                                                                               0        12.3 ± 3.2                                                                             100     0/12                                        ______________________________________                                          T/C is a value which expresses the mean survival day of the treated group      to the mean survival day of the not treated control group by %.          

All of the antibiotics R106 show low toxicity. The results of 50% lethal dose (LD₅₀) obtained when each of representative compounds of the present invention was given to mice intravenously, intraperitoneally and orally are shown in Table 7.

                  TABLE 7                                                          ______________________________________                                         Compound  LD.sub.50 (mg/kg)                                                    No.       i.v.         i.p.    p.o.                                            ______________________________________                                         1         >200         >400    >1000                                           2         >100         >200    >200                                            5         >100         >200    >200                                            7         >100         >200    >200                                            9         >100         >200    >200                                            ______________________________________                                    

From the foregoing biological properties, it is evident that the antibiotics R106 are useful as therapeutic agents for various fungal infections such as candidiasis, histoplasmosis, blastmycosis, etc.

When the compound of the present invention is administered as a drug, the compound can be administered to animals including human as it is, or as pharmaceutical compositions comprising, for example, 0.1 to 99.5%, preferably 0.5 to 90% of the compound in pharmaceutically acceptable non-toxic inert carrier.

As the carrier, solid, semisolid or liquid diluents, fillers and one or more of other aids for formulation can be used. The pharmaceutical composition is desirably administered in a single dose unit form. The pharmaceutical composition of the present invention can be administered orally, intratissularly, topically (percutaneously) or per rectum but, oral compositions and injections are preferred. Needless to say, the compound can be administered in preparations suited for these routes for administration.

It is desired that the dose as the antifungal agent be determined, taking into account conditions of the patient such as age, body weight, etc., route for administration, condition and degree of disease, etc. In proper, it is general to administer the compound of the present invention calculated as an effective ingredient in a range of 10 to 2000 mg per day. If the occasion demands, the dose may be smaller or larger than the above range. When a large dose is required, the dose may be desirably given portionwise several times a day.

Next, the present invention is described in more detail by referring to the examples below.

EXAMPLE 1

One platinum loop from a slant culture of strain No. R106 [deposited at the Fermentation Research Institute of the Agency of Industrial Science & Technology under deposition No. 1938 (FERM BP-1938)] was inoculated in 100 ml of liquid medium (0.67% (w/v) Difco yeast nitrogen base, 2% (w/v) glucose) in a 500 ml Erlenmeyer flask and shaken at 27° C. for 2 days to give a seed culture. The seed culture, 1400 ml, was transferred into a 200-liter fermentor of containing 140 liters of the liquid medium described above followed by fermentation at 25° C. for 63 hours with aeration (100 liters/min.) and agitation (150 rpm). The fermentation broth was centrifuged to separate into the supernatant and the mycelial cake. To the mycelial cake was added 8 liters of acetone. After thoroughly mixing, acetone extract of mycelial cake was obtained. The acetone extract was concentrated under reduced pressure to give 81.5 g of the residue. Methanol was added to the residue to give an active extract. The methanol extract was condensed under reduced pressure to give 65.4 g of the residue. The resulting residue was subjected to a silica gel (made by Merck) column (9 cm×35 cm). The column was eluted with 7 liters of chloroform-methanol (49:1) to give the active fraction. The fraction was condensed under reduced pressure to give 10.6 g of the residue. The resulting residue was subjected to preparative high performance liquid chromatography [column : PREPAK-500/C₁₈ (5.7 cm×30 cm) (manufactured by Waters), mobile phase : 70% (v/v) acetonitrile-water], to give the active fraction. The fraction was condensed under reduced pressure to give 1.5 g of crude R106. The crude substance, 475 mg, was again subjected to preparative high performance liquid chromatography [column : CAPCELL Pak-500/C₁₈ (1 cm×25 cm) (manufactured by Shiseido Co., Ltd.), moving phase : 70 % (v/v) acetonitrile-water] to obtain the active fraction that shows the largest peak in active fractions. The fraction was condensed under reduced pressure to give 370 mg of compound 1 as a white powder. The activity was determined by measuring an antifungal activity against Candida albicans TIMM 0136 according to the paper disk diffusion method using Casitone agar plate. Further the peak in high performance liquid chromatography was detected by measuring ultraviolet absorbance at 230 nm.

EXAMPLE 2

The seed culture, 1000 ml, of strain No. R106 prepared in a manner similar to Example 1, was inoculated in 100 liters of liquid medium (2% glucose, 0.5% ammonium sulfate, 0.15% KH₂ PO₄, 0.05% MgSO₄.7H₂ O, 0.01% CaCl₂, 0.01% NaCl (concentrations are all by w/v), 0.5 μg/ml FeCl₂, 0.5 μg/ml ZnSO₄) in a 200-liter fermentor followed by fermentation at 25° C. for 72 hours with aeration (100 liter/min) and agitation (100 rpm). To the culture was supplemented 20 liters of liquid medium (10% glucose, 2.5% ammonium sulfate, 5% polypeptone, 0.75% KH₂ PO₄, 0.25% MgSO₄.7H₂ O, 0.05% CaCl₂, 0.05% NaCl (concentrations are all by w/v), 2.5 μg/ml FeCl₂, 2.5 μg/ml ZnSO₄), and fermentation was further carried out at 25° C. for 65 hours with aeration (120 liters/min) and agitation (100 rpm).

The thus obtained fermentation broth was centrifuged to separate into the supernatant and the mycelial cake. To the obtained mycelial cake was added 10 liters of ethanol to extract R106. The ethanol extract was concentrated under reduced pressure to remove ethanol and the residue was extracted twice with 1 liter of ethyl acetate. The ethyl acetate extract was concentrated under reduced pressure to dryness, and the residue was dissolved in chloroform. The chloroform solution was subjected onto 1.5 liter of a silica gel column which had been previously saturated with hexane. After washing with 3 liters of hexane, the column was developed and eluted with 6 liters of hexane-isopropanol (7:3). The active fraction was condensed under reduced pressure to give 15 g of the residue. The residue was dissolved in 100 ml of acetonitrile and the solution was divided into 30 and subjected to preparative high performance liquid chromatography [column : SOKEN PAK/C₁₈ (5 cm×50 cm) (manufactured by Soken Chemical Co., Ltd.), mobile phase : 70% (v/v) acetonitrile-water]. The 18 active fractions eluted at the retention time shown in Table 8 were respectively collected and condensed under reduced pressure to give compounds 1 through 18 as white powders in amounts shown in Table 8. The activity detection and the peak detection of high performance liquid chromatography was carried out in the same manner as shown in Example 1.

                  TABLE 8                                                          ______________________________________                                         Compound No. Retention Time (min)                                                                          Yield (mg)                                         ______________________________________                                          1           67.0           3500                                                2           58.8           55                                                  3           60.0           54                                                  4           54.3           96                                                  5           50.6           81                                                  6           42.7           72                                                  7           131.6          1380                                                8           72.5           32                                                  9           62.2           60                                                 10           44.5           12                                                 11           111.4          76                                                 12           112.6          60                                                 13           109.8          24                                                 14           91.6           107                                                15           90.4           42                                                 16           75.0           78                                                 17           146.7          18                                                 18           102.2          15                                                 ______________________________________                                    

                  TABLE 9                                                          ______________________________________                                         Val: valine                                                                    MeVal: N-methylvaline                                                          β-HOMeVal: β-hydroxy-N-methylvaline                                   ##STR4##                                                                      γ-HOMeVal: γ-hydroxy-N-methylvaline                                 ##STR5##                                                                      MeDH.sub.2,3 Val: N-methyl-2,3-didehydrovaline                                  ##STR6##                                                                      MeDH.sub.3,4 Val: N-methyl-3,4-didehydrovaline                                  ##STR7##                                                                      Phe: phenylalanine                                                             MePhe: N-methylphenylalanine                                                   β-HOMePhe: β-hydroxy-N-methylphenylalanine                            ##STR8##                                                                      allo-Ile: alloisoleucine                                                       Leu: leucine                                                                   Pro: proline                                                                   N,β-MeAsp: N,β-dimethylaspartic acid                                  ##STR9##                                                                      ______________________________________                                    

The antibiotics R106 of the present invention are novel antibiotics produced by the strains belonging to the genus Aureobasidium, have low toxicity and high antifugal activity against pathogenic fungi such as Candida Albicans, Cryptococcus neoformans, etc. Therefore, the antibiotics are useful as clinical drugs, for example, therapeutic agents for the treatment of fungal infection. 

What is claimed is:
 1. A process for the production of antibiotic R106 represented by formula (I) below, comprising culturing a strain of Aureobasidium pullulans having all the identifying characteristics of Aureobasidium pullulans FERM BP-1938 or a mutant thereof capable of producing antibiotic R106 in an aqueous nutrient medium containing assimilable sources of carbon, nitrogen, and inorganic substances and recovering the antibiotic from the fermentation medium ##STR10## wherein: R is methyl or ethyl;X₁ is MePhe, β-HOMePhe or Phe; X₂ is allo-Ile, Val or Leu; X₃ is MeVal or Val; X₄ is β-HOMeVal, γ-HOMeVal, MeVal, Val, N,β-MeAsp, β-HOMephe, MePhe, MeDH₂,3 Val or MeDH₃,4 Val. 